Balance Sheet Accounts - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Sep. 30, 2025
Property, Plant, and Equipment [Line Items]
Property, plant and equipment, gross	$ 470,540	$ 462,684
Less: Accumulated depreciation and amortization	(97,239)	(80,169)
Property, plant and equipment, net	373,301	382,515
Land
Property, Plant, and Equipment [Line Items]
Property, plant and equipment, gross	2,995	2,996
Buildings
Property, Plant, and Equipment [Line Items]
Property, plant and equipment, gross	254,859	251,317
Research equipment
Property, Plant, and Equipment [Line Items]
Property, plant and equipment, gross	61,447	62,758
Manufacturing equipment
Property, Plant, and Equipment [Line Items]
Property, plant and equipment, gross	34,182	18,588
Furniture
Property, Plant, and Equipment [Line Items]
Property, plant and equipment, gross	5,813	5,594
Computers and software
Property, Plant, and Equipment [Line Items]
Property, plant and equipment, gross	971	1,064
Leasehold improvements
Property, Plant, and Equipment [Line Items]
Property, plant and equipment, gross	104,462	104,425
Construction in progress
Property, Plant, and Equipment [Line Items]
Property, plant and equipment, gross	$ 5,811	$ 15,942